Carotid artery stenting (CAS) is an emerging procedure that has been used increasingly in recent years. Its growth is due, at least in part, to the perceived advantages of a less invasive treatment for extracranial carotid occlusive disease. However, randomized clinical trial data contrasting the efficacy of CAS and carotid endarterectomy (CEA), the gold standard treatment for carotid atherosclerosis, are not available except in restricted populations. The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) is a continuing effort to contrast the relative efficacy of CAS with CEA in preventing stroke, myocardial infarction or death during a 30-day peri-procedural period, or ipsilateral stroke thereafter in symptomatic and asymptomatic patients with severe carotid occlusive disease. The follow-up period will extend up to four years. Secondary outcomes are to: (1) describe differential efficacy of CAS and CEA in men and women, (2) contrast peri-procedural (30- day) morbidity and post-procedural (after 30-days) morbidity and mortality (3) estimate and contrast the restenosis rates of the two procedures, (4) evaluate differences in measures of health-related quality of life and cost effectiveness, and (5) identify subgroups of participants at differential risk for CAS and CEA. The primary eligibility criterion for CREST is a high-grade stenosis of the carotid artery (>50% by angiogram or >70% by ultrasound for symptomatic disease in patients with transient ischemic attack or ipsilateral non- disabling stroke;>60% by angiogram or >70% by ultrasound for asymptomatic disease). Patients with medical conditions likely to limit their participation during the follow-up or to interfere with outcome evaluation are excluded. A credentialing and training phase precedes randomization at each clinical center where peri- operative morbidity and mortality in this phase has been equivalent to NASCET for symptomatic subjects. 2,500 participants will be randomized at 120 centers. Statistical analysis of the primary outcome will employ standard survival techniques and is designed to provide 90% power to detect an annual difference ? 1.2% in event rates of the primary outcomes. Randomization rates have accelerated to meet and exceed the enrollment goal set by NIH last year and the randomized portion of CREST now includes 962 cases. With the growing use of CAS, CREST may be the last opportunity for an objective evaluation of CEA vs CAS, making its importance even greater. Building on the experience gained in its previously funded years, the CREST investigators have the dedicated investigative team, infrastructure and procedures in place with 108 of the120 clinical sites activated to successfully complete this study.